<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        window.onload = function () {
            var btn = document.getElementById("btnId");
            btn.ondblclick = function () {
                alert("鼠标双击事件");
            };
        };
    </script>
</head>
<body>
<input type="button" value="点击" id="btnId">
</body>
</html>